First Map of Human Fetus Brain Created

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A new map of the human brain during its development in the womb
provides a detailed blueprint of where different genes are active
at this critical stage of in a fetus' life.

This brain atlas yields clues about what makes humans distinct
from other animals, and when disorders like autism first take
root, researchers say.

"This is another installment in our suite of brain atlases to try
to map how all genes are used across the brain and across
development," said study leader Ed Lein, a neuroscientist at the
Allen Institute for Brain Science in Seattle. [ Image
Gallery: Mapping the Brain ]

The institute has previously developed maps of the developing and
adult mouse brain, the developing monkey brain, and the adult
human brain. The new map is the first to look at the
developing human brain — specifically, the developing neocortex,
the seat of higher cognitive functions, Lein told Live Science.
The map is precise enough that scientists can use it to study
different types of cells at various stages of development, he
added.

Snapshot of a developing brain

Researchers created the map using healthy prenatal brains from a
brain bank — a collection of donated human brains. The team used
brain tissue with no known abnormalities or viruses such as HIV.
Researchers took snapshots of brains at two different stages of
prenatal development.

To measure gene activity, the researchers used a powerful tool
known as a DNA microarray, which yields a quantitative
measurement of the activity of every gene in the human genome
simultaneously — about 20,000 genes in total.

The team compared these gene activity results with data from
other species, in particular, the
mouse brain. Mice are widely used in biomedical research as a
model for humans, and these maps could give scientists insight
into how mice brains are similar or different from human brains,
Lein said.

Researchers found some genes that were turned on in the
developing human brain but not in the mouse's brain, or vice
versa. For example, the developing
human brain contains genes that are more active in the
frontal cortex than in the corresponding part of the mouse brain.
The frontal cortex is linked to personality and decision-making.

Clues to brain disorders

The map of a healthy developing brain also provides clues to the
origin of developmental disorders such as
autism, the researchers said. Other studies have revealed
certain genes that are active in autism. Lein's team saw these
genes were turned on in newly generated excitatory neurons (which
activate other neurons) in the prenatal cortex, suggesting
autism may start in the womb, as opposed to later in life.

Taken together, these brain maps paint a picture of where and
when different genes become active in the brain. The genes encode
proteins that perform all the vital tasks inside neurons, giving
rise to the complex cognition of the human brain.

The Allen Institute is one of the private organizations involved
in the BRAIN Initiative (Brain Research through Advancing
Innovative Neurotechnologies), launched by President Obama a year
ago on April 2, 2013.